1. Field of the Invention
The present invention relates to a process for preparing a silver halide dispersion, and more particularly, it relates to a process for forming a fine-grain silver halide dispersion.
2. Description of the Prior Art
When a fine-grain silver halide dispersion has been prepared, a water-soluble polymer such as gelatin or polyvinyl alcohol has been generally utilized as a protective colloid, whereby the silver halide is prevented from coagulating. However, since the protective colloid has low solubility in an organic solvent, it is very difficult for the formed fine-grain silver halide to be uniformly dispersed in an organic solvent.
Polyvinyl pyrrolidone or the polymers disclosed in U.S. Pat. Nos. 3,706,564 and 3,706,565 can be utilized in order to disperse silver halide in an organic solvent after preparing the silver halide in an aqueous solution. That is, the polymer is dissolved in water, a silver halide is prepared in the aqueous polymer solution, the polymer is coagulated and then the aqueous liquid containing the silver halide is redispersed in the organic solvent.
However, often the presence of polymer as a protective colloid is not required. For example, such a polymer is not present in a heat-developable light-sensitive material as disclosed in U.S. Pat. Nos. 3,152,904 and 3,457,075. The light-sensitive material requires the contact of an organic silver salt with a photo-catalyst such as silver halide. In this case, if the polymer as a protective colloid is strongly adsorbed on the silver halide, undesirably the catalytic contact of the organic silver salt with the silver halide is prevented.
On the other hand, if a silver halide is prepared utilizing a polymer which functions as a protective colloid only slightly or without utilizing a polymer as a protective colloid, the silver halide coagulates to form coarse grains, and as a result thereof, it is difficult to catalytically contact the silver halide with an organic silver salt.